I agree, and I'm not criticising the choices that Mark Zuckerberg made at the time. But we are no longer facing the same situation he did. We do now have high productivity, high performance language runtimes. And scaling up has become much cheaper (relative to the number of users you can serve).
That's why I think it can't hurt to remind people of the great lengths to which Facebook had to go in order to deal with the limitations of their chosen platform.
Yeah, I kinda don’t agree with the dichotomy of “you either optimize or you build features”. They’re not exclusive. If you understand the tools and their trade offs you should be able to use the right tools for the job which won’t hinder you in the future.
Of course if all you know is JavaScript, then that requires going a bit outside your comfort zone.
That's why I think it can't hurt to remind people of the great lengths to which Facebook had to go in order to deal with the limitations of their chosen platform.